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NAME

       sched_rr_get_interval - get the SCHED_RR interval for the named process

SYNOPSIS

       #include <sched.h>

       int sched_rr_get_interval(pid_t pid, struct timespec * tp);

DESCRIPTION

       sched_rr_get_interval()  writes  into  the  timespec structure pointed to by tp the round-
       robin time quantum for the process identified by pid.

       The timespec structure has the following form:

           struct timespec {
               time_t tv_sec;    /* seconds */
               long   tv_nsec;   /* nanoseconds */
           };

       If pid is zero, the time quantum for  the  calling  process  is  written  into  *tp.   The
       identified  process should be running under the SCHED_RR scheduling policy.  POSIX systems
       on  which  sched_rr_get_interval()  is  available  define  _POSIX_PRIORITY_SCHEDULING   in
       <unistd.h>.

RETURN VALUE

       On success, sched_rr_get_interval() returns 0.  On error, -1 is returned, and errno is set
       appropriately.

ERRORS

       EFAULT Problem with copying information to userspace.

       EINVAL Invalid pid.

       ENOSYS The system call is not yet implemented (only on rather old kernels).

       ESRCH  The process whose ID is pid could not be found.

CONFORMING TO

       POSIX.1-2001.

NOTES

   Linux Notes
       POSIX does not specify any mechanism for controlling the  size  of  the  round-robin  time
       quantum.   However,  Linux provides a (nonportable) method of doing this.  The quantum can
       be controlled by adjusting the process's nice value  (see  setpriority(2)).   Assigning  a
       negative  (i.e., high) nice value results in a longer quantum; assigning a positive (i.e.,
       low) nice value results in a shorter quantum.  The default quantum  is  0.1  seconds;  the
       degree  to  which  changing  the nice value affects the quantum has varied somewhat across
       kernel versions.

SEE ALSO

       sched_setscheduler(2) has a description of the Linux scheduling scheme.

       Programming for the real world - POSIX.4 by Bill O. Gallmeister,  O'Reilly  &  Associates,
       Inc., ISBN 1-56592-074-0

COLOPHON

       This  page  is  part of release 3.35 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.